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Stefan Oltmann

02/26/2024, 9:29 PM
I try to convince Google bringing Brotli to Kotlin Multiplatform. They already support Kotlin on JVM now, but that’s not enough for a KMP JPEG XL support. Maybe you can add your 👍 to my comment on GitHub, too: https://github.com/google/brotli/issues/1123#issuecomment-1959893441 🙂
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👍🏼 1
@louiscad Your post has inspired me, highlighting the potential for our community to exert influence on crucial JVM-only/Android-only libraries, thereby demonstrating to developers the demand for Kotlin Multiplatform (KMP) support. 😊 One immediate example that comes to mind is the absence of a KMP solution for PDF creation. Perhaps we could select a reputable PDF library like Apache PDFBox and advocate for KMP compatibility there. 🤔
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ephemient

02/26/2024, 9:59 PM
Brotli depends on NIO, PDFBox depends on a ton of Java stuff including reflection
there's not an easy path to making them multiplatform
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Stefan Oltmann

02/26/2024, 10:01 PM
Good point, maybe PDFBox is not a suitable ground for a KMP transformation.
For XMP Core I was lucky that @pdvrieze already took the demanding task making of bringing XML parsing to KMP. The other dependencies already had KMP replacements. I didn't look into PDFBox dependencies, but reflection indeed doesn't sound good. Reflection shouldn't be necessary for a lib like that, either. 🤔
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ephemient

02/26/2024, 10:05 PM
it's to handle different things available in different Java versions
(such as IO)
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Stefan Oltmann

02/26/2024, 10:06 PM
Java NIO should be fully replaceable by kotlinx-io. Maybe even all of the IO needs.
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ephemient

02/26/2024, 10:06 PM
eventually, maybe. definitely not yet, and that introduces interop questions for existing Java users…
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Stefan Oltmann

02/26/2024, 10:09 PM
I try to wrap my head around that. 🤔 Why do we need interop for existing Java users? If a KMP port has the same API and the same parameters lead to the same results, where is the problem?
I might miss something here. For translating Apache Commons Imaging to KMP I first wrote unit test to freeze input->output for a lot of sample files. After I was done (including replacing all IO with kotlinx-IO) I had a pure KMP port that had the very same results for the same inputs as the original JVM version, but on all platforms. If the reflection stuff in PDFBox is to select appropriate API on older JVM versions I would just drop all of that, because Kotlin produces Java 8 bytecode compatible code. It would not support older JVMs then, but that would be fine in my view, because that's all legacy. No need to provide a solution for that in my view.
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louiscad

02/26/2024, 10:24 PM
There is okio for Multiplatform I/O.
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ephemient

02/26/2024, 10:43 PM
NIO is not only an internal usage but also part of the exposed API I believe
yes black 1
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Stefan Oltmann

02/26/2024, 10:43 PM
AFAIK kotlinx-io is a okio fork.
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ephemient

02/26/2024, 10:44 PM
kotlinx-io is rebasing on a fork of but going to be a different API than okio as far as I know
anyhow imo it's certainly possible to fork those libraries to convert to Kotlin multiplatform, but I'm not sure they'd do so upstream…
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Stefan Oltmann

02/26/2024, 10:46 PM
I still don't really understand what you mean with "interop questions for existing Java users"
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ephemient

02/26/2024, 10:47 PM
because they can call into brotli with NIO buffers
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Stefan Oltmann

02/26/2024, 10:47 PM
fork those libraries
I forked Commons Imaging, because the original project is dead. So there is no upstream. For alive libraries that still may change (like Brotli; don't know about PDFBox) a first class support is better.
because they can call into brotli with NIO buffers
Ah, now I got you. You mean that the methods taking Java NIO buffers as arguments of the official API would change to the kotlinx-io equivalent.
Yes, indeed. Support for JVM- or Android-only classes as parameters or return types may be lost during a KMP transformation. That's an interopability concern, right.
For Kim I added them back like here, but how to proceed with a NIO ByteBuffer in a Brotli KMP is a good question, that may be only answered upon taking a closer look. https://github.com/Ashampoo/kim/blob/80028c814de583737f3a95599745d12ca5051df8/src/jvmMain/kotlin/com/ashampoo/kim/JvmKimExtensions.kt#L25-L26
If I find the time I think I will take the challenge to make a Brotli KMP fork and see where the problems are. But first I want to see if Google / eustas are willing to provide first party KMP support. Keeping up to date with a living project may be some work.
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